The present disclosure provides a method for removing cured resin product from subterranean formations in case of inappropriate consolidation, plugging of screens or tubing, and equipment damage.
Hydrocarbon wells are often located in subterranean zones that contain unconsolidated particulates that may migrate within the subterranean formation with the oil, gas, water, and/or other fluids produced by a well penetrating the subterranean formation. As used herein, the term “unconsolidated particulate,” and derivatives thereof, includes loose particulates and particulates bonded with insufficient bond strength to withstand the forces created by the production of fluids through the formation, which may include but are not limited to formation fines and/or proppant particulates. “Formation fine(s),” another term used herein, refers to any loose particles within the portion of the formation, including, but not limited to, formation fines, formation sand, clay particulates, coal fines, and the like. A similar situation can exist in certain wells where particulates referred to as “proppant particulates” may be introduced into the subterranean formation. The proppant particulates may be used in conjunction with hydraulic fracturing to prevent the fractures from fully closing upon the release of hydraulic pressure, forming conductive channels through which fluids may flow to the wellbore.
The presence of these unconsolidated particulates in produced fluids is disadvantageous and undesirable in that the particulates may abrade pumping and other producing equipment and reduce the fluid production capabilities of producing zones. Unconsolidated subterranean zones include those that contain loose particulates and those wherein the bonded particulates have insufficient bond strength to withstand the forces produced by the production of fluids through the zones. “Zone” as used herein simply refers to a portion of the formation and does not imply a particular geological strata or composition.
One way to address the disadvantages caused by unconsolidated particulates is to introduce a resin into the unconsolidated subterranean zone. The term “resin” as used herein refers to any of numerous physically similar polymerized synthetics or chemically modified natural resins including thermoplastic materials and thermosetting materials. In addition to maintaining a relatively solids-free production stream, consolidating particulates also aids in protecting the conductivity of the formation. Such consolidation treatments involve the injection of a liquid resin into the formation and thereafter causing the resin to cure to an infusible state called as thermosetting. The cured resin cements the sand grains or other unconsolidated particulates together by providing high strength, and, ideally, retaining high percentage of initial formation permeability (“Regain Permeability”).
In certain cases, achieving high consolidation strength can be difficult and may require additional resin to account for large amounts of unconsolidated particles. However, if an excess amount of resin composition is pumped to achieve high strength or if there is a delay in the pumping schedule, the resin can cure in undesirable places, including the formation, screens, tubing, and other equipment. The excess resin can also block the formation's permeable channels and reduce the regain permeability. Similarly, consolidated packs of cured resin and particulate can form in undesirable places. The cured resin or consolidated packs can lead to permanent damage to these locations.
Once resin is cured, it can be difficult to remove. Traditionally, a drill bit or similar mechanical method is used to remove cured resin and consolidated packs remaining in the wellbore or in the subterranean formation. However, using these mechanical methods to remove cured resin presents additional challenges and it is not always possible to remove resin from confined spaces or from the surface of equipment.